Ligand Effects on ESR and Optical Properties of Gold Atoms in γ Irradiated Organic Solid Solutions at 77 K

Abstract

Ligand effects on ESR and optical properties of Au0 atoms produced at 77 K in gamma irradiated solid solutions of AuCl/MTHF and AuCl/EtOH with and without HCl were investigated. Four groups of ESR lines were observed at 73 K more clearly around the magnetic fields at about 250, 280, 340, and 400 mT for both gamma irradiated MTHF and EtOH solid solutions with HCl than those without HCl. The values of a and g(J) calculated by Breit-Rabi analysis showed a remarkable dependence on the solvent polarity. It was confirmed that the signals were the hyperfine quartet corresponding to the transitions between the Zeeman levels of Au0 atoms with nuclear spin of 3/2 in the ground state, 2S(1/2). It was also confirmed that Au0 atoms produced after gamma irradiation were located in the nuclear environment of isotropic interaction with surrounding ligand molecules. Delocalization of the unpaired spin density of Au0 onto ligands is found to be as large as one in the case of Cu0 atoms. Our previous hypothesis of the occurrence of configuration mixing of d valence orbital into the wave function of the atom in its 2S(1/2) was strongly supported. The dependence of the ESR, optical absorption, and the steady-state emission and excitation characteristics on solvent polarity was cleared in this study. We observed two kinds of emissions i.e., a band at 385 nm and a set of emission bands at 456, 482, 484, and 520 nm. These correspond to two bands out of the six kinds of emissions observed previously. The bands were attributed to exciplex (Au0 x Ln...Au+)* and the excited Au0 atoms trapped in a large cavity, respectively. The negative counterion of Au+ of the gold compound plays an important role for the formation of the exciplexes.

Electron spin resonance (some chemical applications)

“…Additionally, there were Au(0) atoms that showed a hyperfine interaction with magnetic nuclei from the matrix. 162 By means of ENDOR spectroscopy, the properties of Cu 21 and (VO) 21 cations stabilised in polymers were investigated. It was found that the origin of the ENDOR signal is mainly due to anisotropic interactions between the unpaired spin and the nuclei of matrix atoms, such as water.…”

Effects of UV Irradiation on ESR and Optical Properties of Cu(II) Ions in Organic Solid Solutions Containing CuCl at 77 K

“…As a fundamental research to elucidate the function and effects of metal ions and/or atoms in biological systems, we have been investigating the ESR and optical properties of 1B metal atoms produced radiation-chemically by reducing their mono cations in solid solutions [4][5][6][7][8][9][10][11][12]. In the series of our previous studies, formation of metal atoms, Cu 0 , Ag 0 and Au 0 in irradiated solid solutions containing their mono cations were evidenced by ESR spectra that exhibited duplicate quartets [10], duplicate doublets [8] and quartet [12], respectively. The values of the hyperfine splitting, a and the gyromagnetic ratio for the electron shell, g J were evaluated from the Breit-Rabi equations that were applied for the case of isotropic forces of interaction between trapped atoms and ligands.…”